Search Results (2,927)

The Xinqiao Cu-S polymetallic deposit is located in the Tongling ore concentration area of the Middle-Lower Yangtze River metallogenic belt. The orebodies consist of skarn orebodies and stratiform sulfide orebodies, but the genetic link between them remains controversial. In this study, magnetite was used as a proxy to systematically constrain the hydrothermal evolution from the intrusion to the contact zone and further to the stratiform orebodies. A representative drill hole (E603) was logged, and samples were systematically collected from the Jitou pluton outward to the contact zone. Composite samples from the 8–28 m interval were crushed and prepared as resin mounts for integrated TIMA automated mineralogy, BSE textural observation, and in situ LA-ICP-MS trace element analysis. Five types of magnetite (Mt1 to Mt5) were systematically identified. Mt1 occurs as inclusions within feldspar in the quartz monzodiorite. It exhibits typical magmatic magnetite characteristics and contains grid-like ilmenite exsolution, indicating crystallization during the late magmatic stage. Mt2 is distributed in the interstices of magmatic minerals, commonly showing hematitization and replacement of ilmenite exsolution lamellae by titanite. Its trace element geochemistry displays magmatic–hydrothermal transitional features. Mt3–Mt5 in the skarn and stratiform orebodies are paragenetic with retrograde alteration minerals (e.g., epidote, chlorite, and actinolite) and sulfides, and are characterized by low Ti, Al, and V contents and high Mg, Mn, and Sn contents, indicating a hydrothermal origin. From Mt3 to Mt5, (Ti + V) and (Al + Mn) decrease, while Zn and Mn increase, accompanied by a decrease in the (Si + Al)/(Mg + Mn) ratio. This reflects a trend of decreasing fluid temperature and progressively enhanced wall-rock buffering. The Mg-in-magnetite geothermometer yields relatively consistent results for Mt1–Mt3, but anomalously high temperatures for Mt4–Mt5. This suggests that the elevated Mg activity in the fluid, caused by reaction with carbonate wall rocks, can significantly influence the calculated temperatures. Therefore, this geothermometer should be used cautiously for magnetite in the outer skarn zone and interpreted in combination with other temperature constraints. The textures, paragenetic mineral assemblages, and trace element characteristics of magnetite collectively reveal a continuous mineralization process linking the skarn and stratiform orebodies at Xinqiao, providing robust mineralogical and geochemical evidence for the contribution of Yanshanian magmatic–hydrothermal activity to the stratiform mineralization. Full article

Coal preparation tailings from the K18 seam of the Abayskaya mine were evaluated as a potential secondary source of critical rare earth elements (REEs). The study showed that REEs are predominantly associated with the mineral fraction of coal; therefore, during beneficiation, approximately 70% of their total content is transferred to flotation tailings. The concentrations of valuable elements in the tailings are as follows (g/t): Li—65; Sc—16; Y—17; Yb—2.5; V—135; and Ti—2293. These values significantly exceed the Clarke values and are comparable to those of some low-grade primary ores, indicating the potential of coal preparation wastes as a technogenic raw material for critical elements. To extract REEs from the resistant aluminosilicate matrix, a fluorine–ammonium sulfate thermochemical activation method was proposed. Using a probabilistic–deterministic experimental design approach, a mathematical model of the process was developed and optimal parameters were determined (400 °C, 120 min, (NH₄)₂SO₄ consumption—140% relative to Al, NH₄HF₂ consumption—110% relative to Si), providing a feed liberation degree (by Al extraction) of up to 94%. Under optimal conditions, high leaching efficiencies of key elements were achieved: Sc (95%), Y (100%), Yb (100%), and Li (100%). The results demonstrate the significant potential of coal preparation tailings as a secondary resource of rare earth elements and confirm the efficiency of fluorine–ammonium sulfate technology for processing this type of technogenic waste. Full article

To investigate the mechanism of texture formation during the cold rolling of Ti-3Al-2.5V tubes for aerospace hydraulic systems, this study examines the microstructure at various locations of two deformation cones with ‘Q’ ratios of 1.055 and 1.300, respectively, in a single cold-rolling pass, revealing their continuous texture evolution. The results indicate that the cold-rolling texture primarily forms during the sinking section. A higher ‘Q’ ratio leads to a stronger tendency for the c-axis of grains to align parallel to the radial direction of the tube, resulting in enhanced radial texture intensity. Beyond influencing texture through dislocation slip, a higher ‘Q’ ratio also elevates the Schmid factor for {10$\stackrel{\mathrm{-}}{1}$2} twinning. This twinning mechanism primarily forms the radial texture by altering the stress state. Consequently, this change not only facilitates twin activation but also modifies the rotation direction of grains during the twinning process. Compared to the cone with a ‘Q’ ratio of 1.055, the deformation cone with a ‘Q’ ratio of 1.300 contains a greater number of twins oriented along <0001>//RD, leading to a stronger radial texture in the tube. Full article

In this work, for the first time, we applied and determined the mechanical characteristics of protective coatings made of high-entropy alloy (TiZrVCrAl)N with different architectures onto the surface of Ti-6Al-4V alloy with the initial coarse-grained and ultrafine-grained structure using arc physical vapor deposition. We designed and prepared three coating architectures: a monolayer nitride coating (TiZrVCrAl)N, a multilayer coating consisting of nine alternating layers of TiZrVCrAl and (TiZrVCrAl)N, and a multilayer coating consisting of 720 alternating layers of (TiZrVCrAl)N and TiN, with a total thickness not exceeding 2 microns. We evaluated their protective performances by nanoindentation and scratch tests. Importantly, the effect of the substrate microstructure on the coatings’ performance is investigated by comparing their mechanical behavior on coarse-grained and ultrafine-grained Ti-6Al-4V. Our experimental results show that the coating performance improves with increasing number of layers in the coating, and this effect is even more pronounced for the multilayer coating deposited on the ultrafine-grained titanium alloy substrate. We also find that the (TiZrVCrAl)N/TiN (720 layers) multilayer coating deposited on the UFG Ti-6Al-4V alloy substrate exhibits the highest H/E- and H³/E²-values, indicating the coating’s high innovative potential for performance in extreme conditions. The origins of this phenomenon are analyzed and discussed. Full article

Thin wall composite fan blades in aircraft engines demand designs that ensure structural integrity under operational loads while resisting foreign object damage and bird strikes. This study presents a finite element investigation of thin wall composite blades with metal leading edge caps, modeled through parametric coupon analyses under static flexure loading using ANSYS APDL. Three metallic leading edge caps, Ti-6Al-4V, Inconel 718, and 15-5 PH stainless steel, were combined with IM7/8551-7 carbon fiber composites. Parametric variations included changes in metal cap material, geometric designs of the joint, and other things. Performance was evaluated in terms of failure stress, interlaminar shear strains, interface integrity, and failure margins. Results reveal that cap design and cap material critically govern structural response, with distinct interchanges between strength-to-weight efficiency, interface stresses, and interlaminar shear strain. Optimal designs reduced interlaminar shear strain levels in thin wall composite blades, while retaining adequate stiffness and strength. The results underscore the importance of interface design for effective load transfer and provide design guidelines for lightweight, damage-tolerant thin wall composite fan blade structures. Full article

The synergy between additively manufactured (AM) polymers and functional PVD coatings is crucial for advanced applications, yet the reliability of these hybrid systems is dictated by the residual stresses induced during deposition. This work presents the first in-depth, nanoscale profiling of residual stresses in Ti6Al4V and SS316 coatings on 3D-printed Acrylonitrile Styrene Acrylate (ASA) and Silicon (Si) substrates. A cutting-edge methodology combining Focused Ion Beam (FIB) milling with Digital Image Correlation (DIC), rigorously interpreted through the non-integral eigenstrain theory, is employed. Our findings reveal a consistent pattern of compressive stresses near the coating surface but expose a significant tensile stress peak at the coating-substrate interface, a feature not observed on reference silicon substrates. High-resolution electron microscopy and elemental analysis suggest that this stress concentration is associated with the presence of a thin, brittle oxide interlayer formed on the substrate surface. Furthermore, this study quantifies the dominant effect of the low-stiffness polymer substrate, which leads to a strain relief magnitude an order of magnitude higher than in rigid substrates. This work provides critical quantitative data on the failure-driving mechanisms in these emerging material systems and establishes a robust, optimized metrological protocol for their characterization. Full article

This work focuses on obtaining a titanium nitride coating on the surfaces of titanium and its alloy powders using a novel method, self-shearing reactive milling, under a nitrogen pressure of 50 bar. The Ti, Ti6Al4V, and Ti-5553 spherical powders were milled for up to 10 h at ambient temperature without grinding balls. As a result of the experiments, a thin, brittle TiN coating formed on the powders’ surfaces. The cross-sections of the milled powders reveal that the TiN layer thickness is in the nanometer range (about 500 nm). By analyzing the sequence of X-ray diffraction patterns, it is evident that only for the Ti6Al4V powder milled for 10 h, two peaks are observed that can be attributed to a TiN phase. On the other hand, Raman spectroscopy revealed characteristic TiN spectra even for samples collected at the initial stage of self-shearing reactive milling. An important aspect of the experiment was the preservation of the spherical shape of the milled powders, which makes them a potential feedstock for additive manufacturing of functionally graded biomaterials. Full article

Titanium and its alloys are widely used in dental implantology due to their favorable mechanical properties and well-documented long-term clinical performance. Among them, Ti-6Al-4V is particularly common in load-bearing applications. Nevertheless, a growing body of experimental and clinical evidence suggests that Ti-6Al-4V implants cannot be regarded as biologically inert in all patients. Adverse tissue responses, such as impaired healing, chronic peri-implant inflammation, and unexplained implant failure, have been reported even in the absence of classical risk factors, including infection, mechanical overload, or confirmed metal allergy. This critical review challenges the prevailing assumption that these complications are driven primarily by mechanical or immunoallergic mechanisms. Instead, oxidative stress is proposed as a central and unifying factor underlying adverse tissue reactions to Ti-6Al-4V dental implants. Corrosion, tribocorrosion, and mechanical wear lead to the release of titanium-, aluminum-, and vanadium-containing particles and ions, which promote excessive generation of reactive oxygen species at the implant–tissue interface. The resulting redox imbalance disrupts bone remodeling, impairs osteogenic differentiation, and maintains a pro-inflammatory microenvironment. Importantly, pathology arises not merely from increased reactive oxygen species production, but from the failure of local antioxidant defense systems to counteract this burden. Insufficient enzymatic and transcriptional antioxidant responses result in persistent redox imbalance, sustained innate immune activation, and progressive tissue intolerance. Oxidative stress is therefore conceptualized not as a secondary byproduct of inflammation, but as a primary driver of immune dysregulation through chronic macrophage activation and inflammasome signaling. This redox-driven feedback loop amplifies tissue damage and compromises long-term osseointegration independently of classical adaptive immune sensitization. Recognizing oxidative stress as a key determinant of implant–tissue interactions offers a more coherent framework for understanding implant-related complications and underscores the need for redox-aware biomaterial strategies and individualized patient risk assessment. Full article

Additive manufacturing (AM) of Ti-6Al-4V alloy is widely used in aerospace and medical fields due to its excellent strength and corrosion resistance. However, the microstructural heterogeneity induced by the AM process often results in fatigue properties inferior to those of their forged counterparts. Synchrotron Radiation Computed Tomography (SR-CT) was employed to conduct an in situ three-dimensional investigation of fatigue damage evolution in Ti-6Al-4V alloy fabricated via laser powder bed fusion (LPBF). Experimental results revealed phenomena of crack bridging and deflection, accompanied by the consistent presence of local high-density zones (LHDZs) throughout the fatigue damage progression. Combined with quantitative analysis of crack propagation rates, the influence of LHDZs on fatigue damage evolution was analyzed, and the relationship between AM processes, LHDZs, and fatigue damage was discussed. The results indicate that the basket-weave α-phase microstructure in Ti-6Al-4V prepared by LPBF exhibits a high correlation with the distribution of LHDZs, and the orientation of LHDZs aligns with the crack propagation direction. By adjusting process parameters such as cooling rate and temperature gradient, the formation of LHDZs can be modified, thereby influencing the fatigue properties of the material. This provides theoretical support for achieving process optimization of the fatigue properties of Ti-6Al-4V alloy prepared via LPBF. Full article

This study examines the effect of vanadium addition on the microstructure and mechanical properties of low-cost powder metallurgy Ti-4Al-2Fe-3Cu alloys. Alloys with and without 6 wt.% V were fabricated by hot extrusion of blended elemental powders followed by vacuum heat treatment. Microstructural analysis revealed that the base alloy exhibits a coarse lamellar α/β structure, while vanadium addition promotes a refined basketweave morphology with a significantly higher β-phase fraction, increasing from 28.1% to 46.2%. Energy-dispersive spectroscopy confirmed preferential partitioning of Fe, Cu, and V into the β phase. Mechanical testing showed that the addition of 6 wt.% V markedly enhances strength, increasing yield strength and ultimate tensile strength from 1122 MPa and 1214 MPa to 1291 MPa and 1349 MPa, respectively, while maintaining comparable tensile ductility (~3.5%). The strength improvement is attributed to α-plate refinement, increased β-phase fraction, and solid-solution strengthening of the β phase. These results demonstrate that vanadium addition is an effective approach for improving the strength of low-cost PM titanium alloys without compromising ductility. Full article

Titanium and its alloys are widely used in endoprostheses. The naturally formed titanium dioxide film on titanium surfaces improves chemical stability and enhances implant biocompatibility. However, oxidised titanium surfaces may also promote bacterial adhesion and biofilm formation, contributing to implant-associated infections. Therefore, surface modification represents a key strategy for controlling microbial–implant interactions. This article focuses widely used titanium alloy Ti-6Al-4V treated with a laser beam, which induces surface colour changes as a result of oxide formation. Laser processing enables controlled formation of micro- and nanoscale features, structural reconstructions, and defects that may influence the surface electrical charge and, consequently, cell immobilisation. Thus, the surface colour, electrical potential, and cell immobilisation capacity are likely interrelated. From a manufacturing perspective, titanium oxide colouring facilitates quality control and process reproducibility, as surface colour provides a rapid, non-destructive visual indicator of oxide thickness and treatment consistency. This study aims to identify correlations among surface colour, electrical potential, and cell immobilisation capacity on laser-treated titanium alloys. A relationship between the optical properties, electronic structure, and biological response of laser-processed titanium oxide films is established. Specifically, the blue colour saturation of the oxide film is inversely correlated with the electron work function. A more saturated blue corresponds to a lower work function, indicating a higher positive surface charge density. This shift is attributed to changes in electron affinity, likely resulting from laser-induced structural reconstruction and defect formation within the oxide layer. The proposed changes in electronic structure are supported by modifications in the electronic density of states, analysed using near-threshold photoelectron spectroscopy. The biological response is directly linked to these physical changes: enhanced immobilisation of yeast (Saccharomyces cerevisiae) cells on the treated alloy surface correlates with the electron work function. These results may assist in the development of controlled titanium oxide surfaces with enhanced biocompatibility. Full article

Although processing windows have been widely reported for LPBF Ti-6Al-4V, the distinct roles of laser power, scanning speed, and hatch distance remain unclear beyond VED-based comparisons. In this work, the distinct effects of laser power, scanning speed, and hatch distance on the microstructural evolution and mechanical response of laser powder bed fusion (LPBF) Ti-6Al-4V (Ti64) are investigated within a stable processing window with comparisons among different parameter combinations at a comparable VED. A total of 56 processing conditions were designed, and microstructure/texture and properties were characterized by OM/SEM, EBSD, microhardness (HV0.5), and hole-drilling residual stress measurements. Within the selected processing window, prior-β grain morphology, α’ martensite thickness, texture, microhardness, and residual stress exhibit distinct sensitivities to different processing parameters. Specifically, lower scanning speeds and smaller hatch distances promote more continuous <001>β epitaxial growth, whereas higher scanning speeds or larger hatch distances produce fragmented prior-β grains. The α’ lath thickness shows the strongest dependence on scanning speed with a secondary influence from hatch distance, while laser power mainly provides an overall thermal modulation. Furthermore, the macroscopic α (0002) texture is mainly governed by the β solidification texture, with α-variant selection playing a secondary, amplifying role. In addition, microhardness correlates with α’ martensite thickness following a Hall–Petch equation. The peak residual stress is more sensitive to scanning speed, while bulk residual stress varies more significantly with hatch distance. These findings demonstrate that process parameters, in addition to VED, can guide microstructural control and mechanical optimization in LPBF Ti64 alloy. Full article

Magnetite is extensively developed within various alteration zones of the mining district. Some magnetite is closely associated with copper mineralization, possessing significant research value. The Duobuza Cu (Au) deposit is a typical porphyry-type deposit within the Bangong Co-Nujiang metallogenic belt and was the first porphyry Cu-Au deposit discovered in the Duolong copper–gold ore district. Currently, this deposit contains copper resources exceeding 3 million tons @0.46%, with associated gold resources exceeding 80 tons @0.19 g/t. This study focuses on magnetite from the Duobuza deposit. Through field geological logging and microscopic identification combined with electron microprobe analysis (EMPA) and in situ LA-ICP-MS testing, mineralogical and mineral chemical research on magnetite is conducted. This research aims to elucidate the genesis of magnetite in the Duobuza deposit and its implications for mineral exploration. Five magnetite types with different occurrences can be distinguished in the Duobuza deposit: Mt₁ is magmatic magnetite; Mt₂, Mt₃, Mt₄, and Mt₅ are hydrothermal magnetite, with Mt₅ being closely associated with copper mineralization. Mt₁ is relatively enriched in Ti, V, Al, and Cr but depleted in Mn and Si; Mt₂ is relatively enriched in Ti and Al but depleted in Si and Cr; Mt₃ is relatively enriched in Al but depleted in Mg; Mt₄ is relatively enriched in Ti, Al, V, Zn, and Mn; and Mt₅ is relatively enriched in Mg, Si, Ti, Al, Mn, and Zn but depleted in Cr. Based on the Al + Mn vs. Ti + V discrimination diagram, magnetite formed in a medium- to high-temperature environment, with hydrothermal magnetite Mt₄ forming at the lowest temperature. Vanadium (V) content can be used to estimate the oxygen fugacity (fO₂) during mineralization. Mt₁ exhibits the highest V content, indicating relatively low oxygen fugacity, whereas Mt₄ shows the lowest V content, suggesting relatively high oxygen fugacity. Mt₅ has a higher V content compared to other early-stage hydrothermal magnetites, suggesting that a lower fO₂ formation environment favors the precipitation of metal sulfides in the mining district. Trace element analysis of magnetite from the Duobuza, Bolong, and Naruo mining districts reveals that magnetite from all three deposits is enriched in Si and Al and depleted in Ca and Ni. Magmatic magnetite from the Naruo and Duobuza deposits exhibits similar elemental distribution patterns. Hydrothermal magnetite from the Duobuza deposit shows significantly higher Ti and V contents compared to magnetite from the Bolong and Naruo deposits. Full article

Multi-material structures based on titanium alloys represent a promising approach for the fabrication of functionally graded orthopedic implants capable of combining high mechanical strength with reduced stiffness to minimize the stress-shielding effect. In the present work, multi-material Ti15Ta/Ti6Al4V specimens were fabricated by laser powder bed fusion (L-PBF) for the first time, and the processing parameters of the transition zone were systematically optimized. Three regimes were investigated: baseline (93 J/mm³), double scanning (186 J/mm³), and reduced speed (116 J/mm³). The microstructure and elemental distribution were examined by SEM and EDS; mechanical properties were evaluated through tensile testing and microhardness measurements; biocompatibility was assessed using osteoblasts and gingival fibroblasts. The double scanning regime provided the highest density of the transition zone (99.49%). Tensile failure of the specimens occurred in the Ti15Ta region, confirming the quality of the metallurgical bond. The ultimate tensile strength ranged from 534 to 543 MPa with an elongation at break of 15.7–16.4%. Heat treatment at 875 °C led to the formation of an equilibrium lamellar microstructure and smoothing of the interface. Cell viability on both alloys exceeded 88% as confirmed by flow cytometry and remained above the 70% non-cytotoxicity threshold defined by ISO 10993-5. The obtained results demonstrate the technological feasibility of fabricating multi-material Ti15Ta/Ti6Al4V structures and achieving high-quality metallurgical bonding, which constitutes a necessary first step toward the development of functionally graded orthopedic implants. Full article

Aiming at the contradiction between forming quality and efficiency in the existing research on thick-layer laser powder bed fusion (LPBF) manufacturing of Ti6Al4V, this study focused on the influence of near-circular keyhole defects caused by scanning speed on the short-term mechanical properties of Ti6Al4V alloy manufactured by high-efficiency LPBF with a 100 μm layer thickness, the build rate of which reached 14 mm³/s. When the scanning speed decreased to 800 mm/s, the relative density decreased from 99.87% to 99.27%, and the maximum pore size increased from 19.6 μm to 87.2 μm. Under the conditions of high relative density (above 99.8%) and maximum pore size less than 20 μm, the annealed Ti6Al4V samples could achieve a tensile strength of 1009.7 MPa, a yield strength of 914.0 MPa, an elongation of 15.2%, and an impact toughness of 41.71 J/cm². With the increase in porosity and a maximum pore size exceeding 50 μm, the tensile strength became more unstable and exhibited a declining trend, while the impact toughness decreased by more than 5%. This is mainly attributed to the stress concentration around large-sized pores, leading to the easy generation of long and deep cracks at the edges and reducing the material’s ability to resist crack initiation and propagation. Full article